Knauf Fiber Glass Gmbh

John M Beall

A lateral varactor is fabricated with a recess structure that provides staggered punch-through points, enabling the varactor to be tuned through punch-through without significant non-linearities in either capacitance or Q. The lateral varactor (30) includes a cathode (32) and an anode (40) disposed on the surface of an active layer (12). The anode (40) includes a surface section (45), and a recess section (46) disposed within a recess area (50). This recess structure results in a greater active layer depth under the anode surface section (45) than under the anode recess section (46). As a result, as reverse-bias voltage on the anode increases, the depletion region (60) reaches punch-through under the anode recess section (46) prior to reaching punch-through under the anode surface section (45). As a result, varactor capacitance depends upon the contributions associated with each anode section and sidewall capacitance, so that the abrupt impedance changes caused by tuning the varactor through a punch-through point is reduced, and varactor tuning is made more continuous.

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Dallas, TX, United States of America

John M Beall